[tor-bugs] #33545 [Core Tor/Tor]: assertion failure when "all zero" client auth key provided

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#33545: assertion failure when "all zero" client auth key provided
------------------------------+------------------------------------
     Reporter:  mcs           |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:  Tor: 0.4.4.0-alpha-dev
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 While doing some Tor Browser testing for Sponsor 27, I experienced the
 following after I intentionally used an incorrect client auth key for a v3
 onion service:
 {{{
 ... [err] tor_assertion_failed_: Bug: src/feature/hs/hs_descriptor.c:1423:
 decrypt_descriptor_cookie: Assertion !fast_mem_is_zero((char *)
 client_auth_sk, sizeof(*client_auth_sk)) failed; aborting. (on Tor 0.4.4.0
 -alpha-dev 1da0b05a5cace6ed)
 }}}

 As it turns out, I happened to enter a key that is consists entirely of
 zero bits. This is an unusual thing to do, but I do not think tor should
 exit.

 Steps to reproduce in Tor Browser:
 1. Try to load an http or https page for a v3 onion service that requires
 client authentication, e.g., dgoulet's test server.
 2. Enter 56 'A's when prompted for a client auth key.

 Result: tor exits due to the assertion failure. Behind the scenes, the
 browser installs the key via a control port command like the following:
 {{{
 onion_client_auth_add <onion-addr>
 x25519:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=
 }}}
 and then tries to access the onion service again (page reload).

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33545>
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